photo-engraving

Century Dictionary and Cyclopedia

1. n. A common name for many processes by which a photograph may be made to afford a plate-matrix from which can be taken prints in ink corresponding to the original of the photographic image. These processes depend upon the property, possessed by potassium bichromate and analogous chemicals, of rendering insoluble, under the action of light, gelatin or some similar body with which they are compounded. By applications of this property, varying according to the process, a picture or design can be produced on a metal surface, and the blank places etched out with acid; or a matrix in relief can be formed, from which an electrotype plate can be made in ordinary ways. In general, the term photo-engraving is limited to a relief-block or -plate produced by photographic means for printing in an ordinary printing-press, to the art of making such blocks, and to prints from them; while the term photogravure is commonly applied to a photographically engraved plate in intaglio from which prints may be taken in a copperplate-press, to the art of making such an incised plate, and to a print from it. In the Gillet process a zinc plate coated with asphaltum is exposed beneath a negative, and those portions unchanged by light-are dissolved. The zinc is then etched. Photographs are reproduced in the form of half-tone plates for use in the printing-press by several methods, all of which depend upon breaking up the surface of the picture by dark lines in regular series. A gelatin film on which such a series of lines has been photographed is placed between the sensitized surface which is to receive the impression and a positive picture. The resulting print will consist of the subject appearing in half-tone on a ground of lines, and from it a typographical matrix is prepared in the usual ways. (For an example of a half-tone plate, see cut under dekadrachm.) Also called photographic engraving, photographic-process printing, photographic process. See photoetching (Gillet process), and compare heliotypy and photogravure.
2. n. A print or plate made by photography and developed by etching for use on a type-printing press.

GNU Webster's 1913

1. n. The process of obtaining an etched or engraved plate from the photographic image, to be used in printing; also, a picture produced by such a process.

WordNet 3.0

1. n. an engraving used to reproduce an illustration